1. Field of Invention
The present invention relates to a map displaying apparatus which allows an operator to input the destination of a vehicle into a map even if the operator does not know the exact location of the destination on the map.
2. Prior Art
One example of a map displaying apparatus is an on-vehicle navigation apparatus. A navigation apparatus is used for displaying both the present position and the destination of a vehicle on a map to ensure smooth running of the vehicle at night as well as in a strange town.
FIG. 9 is a block diagram showing a prior art navigation apparatus disclosed in Japanese Patent Preliminary Publication(KOKAI) No.1-119898. In the figure, a displayer 1 displays a map where the destination of a vehicle is specified by an operator through a destination setting section 2. A map memory 3 stores therein information on road maps and road segments that constitute the road maps. A travel-time memory 4 stores therein the time required for traveling the road segments according to months of the year, days of the week, and hours.
An area-to-be-retrieved defining section 5 calculates a point-to-point distance on a map between the present vehicle location and the destination of the vehicle, and then defines an area where a group of road segments to the destination are retrieved in accordance with the calculated point-to-point distance. A route retrieving section 6 retrieves all possible combinations of road segments for the road maps stored in the map memory 3, which possible combinations of road segments lead the operator all the way from the present vehicle location to the destination. A route-extracting section 7 extracts a minimum-travel-time route in terms of the time required for traveling respective segments, which minimum-travel-time route requires a minimum time to travel from the present vehicle location to the destination. A present vehicle location detecting section 8 calculates an accumulated azimuth and an accumulated distance resulted from the running of the vehicle to determine a calculated present vehicle location on a map. A highlight signal producing section 9 produces a signal used for highlighting both the minimum-travel-time route and the calculated present vehicle location on the displayed road map. A guiding section 10 supplies the displayers with the minimum-travel-time route and the signal for highlighting the calculated present vehicle location on the road map, and stores the time spent to actually travel the respective road segments into the travel-time memory 4.
FIG. 10 shows the structure of map data stored in the map memory 3. Data A is map data on a country-wide level. Data B is map data on a regional level where the whole country is divided into a plurality of large regions. Data C is map data on a area level where each of the plurality of regional is further divided into a plurality of areas. FIGS. 11 and 12 show the destination setting section 2 provided on the front panel of the displayer 1 of a prior art on-vehicle navigation apparatus. In FIG. 11, a power key 801 is used to turn on and off the apparatus. A destination key 802 is used to set a destination and to check the destination on display. A parameter key 803 is used to set various conditions when guiding the vehicle along the routes selected. A start key 804 is used to start guiding a vehicle along the selected route. A scroll key 805 is to scroll the map displayed on the displayer 1 upwardly and downwardly as well as leftward and rightward.
The prior art on-vehicle navigation apparatus will now be described in terms of its operation when setting a destination. When the destination key 802 is pressed, an option menu, not shown, appears on the displaying screen for an operator to select either "SET" or "CHECK". Pressing "SET" brings the country-wide map, not shown, on the displaying screen and prompts the operator to select a regional map therefrom. Upon selecting a regional map, the corresponding regional map appears on the displayer 1, the sample of which being shown in FIG. 11. Upon selecting an area from the regional map on display allows an area map as shown in FIG. 12 to be displayed.
The prior art on-vehicle navigation apparatus operates in a manner illustrated by the flowchart in FIG. 13.
A country-wide map is displayed at step 901, and a check is made at step 902 to determine whether a regional map has been selected. If the result is NO at step 902, then the program iterates step 902; if YES, then the program proceeds to step 903 where the selected regional map is displayed. Then, the program proceeds to step 904 where a check is made to determine whether an area map has been selected. If the result is NO at step 904, then step 904 is repeated; if the result is YES, then the program proceeds to step 905 where the selected area map is displayed on the displayer. Thereafter, a check is made at step 906 to determine whether an enlargement key, not shown, has been pressed. If the enlargement key has been pressed, then the a detailed map is displayed at step 907 and then the program returns to step 906.
If the enlargement key has not been pressed, then the program proceeds to step 908 where a check is made to determine whether a reduction key has been pressed. If the result at step 908 is YES, the program proceeds to step 909 where a larger area map including area map displayed at step 905 is displayed and then the program returns to step 906.
If it is determined that the reduction key has not been pressed, the program proceeds to step 910 where a check is made whether the scroll key has been pressed. If the result at step 910 is NO, then the program proceeds to step 911 where the program performs scrolling of map and then returns to step 906.
If the answer is NO at step 910, the program proceeds to step 912 where a check is made to determine whether the "SET" has been pressed. If the answer is YES at step 912, the position coordinate of the center of the displayed map is registered at step 913 as the coordinate of the destination before completing the destination setting. If the answer at step 912 is NO, a check is made at step 914 to determine whether "CANCEL" has been pressed. If the answer at step 914 is YES, then the destination setting is interrupted and a series of steps for displaying a map is terminated. If the answer is NO at step 914, then the program returns to step 906 to thereby continue to determine whether any key input is made.
The above-mentioned prior art on-vehicle navigation has a drawback that an operator must know the exact location of the destination on the map. The telephone number of the destination, area codes, or postal codes are of no help.